According to a recent trend, a communication system has an increased service frequency band, and cells having decreased radiuses for high speed communications and increased telephone traffic. This may cause many problems when applying the existing centralized cellular radio network method as it is. More concretely, a configuration of a radio link has a degraded flexibility due to a fixed location of a base station. This may cause a difficulty in providing efficient communication services in a radio environment where traffic distributions or requested telephone traffic are severely changed.
In order to solve these problems, has been proposed a Multi-Hop relay system. This multi-hop relay system has the following advantages. Firstly, a cell service area may be increased by covering partial shadow areas occurring inside a cell area, and a system capacity may be increased. Furthermore, an initial situation requiring less service is implemented by using a relay. This may reduce the initial installation costs.
FIG. 1 is a view schematically illustrating a relay communication system.
A base station 101 forms a channel link with terminals 105 and 107. Here, the base station 101 may directly form a channel with the terminal 105 through a link 121, or may form a channel with the terminal 107 through a relay 103. A downlink channel 123 formed from the base station 101 to the relay 103 is called a backhaul link. The backhaul link 123 includes Relay-Physical Downlink Shared Channel (R-PDSCH) through which data is transferred from the base station 101 to the relay 103, and Relay-Physical Downlink Control Channel (R-PDCCH) through which control information is transferred.
In a sub-frame where the base station performs a downlink backhaul to the relay, control information and backhaul data of the relay have to be transferred. This may cause a difficulty in transmitting and receiving the control information and the backhaul data together with a downlink link sub-frame between the base station and a terminal. Furthermore, there is a limitation in controlling resource allocation according to a traffic amount of downlink backhaul data.